1. The Field of the Invention
The present invention is in the field of devices for attaching bodily tissue to a bone. More specifically, the present invention is directed to an anchor device for attaching an end of a bodily tissue, such as a tendon, ligament or replacement graft ligament under tension to a bone for repairing or replacing a damaged tendon or ligament.
2. The Relevant Technology
Damaged tissues, such as torn or ruptured ligaments, are commonly replaced by grafts from other replacement tissues such as tendons, muscles or artificial materials. While medical techniques in replacing damaged ligaments have greatly advanced over the past few years, one problem with presently used ligament replacement and repairing techniques is the need to provide a firm and reliable fixation point for the graft replacement tissue.
In ligament replacement surgical procedures, particularly in cruciate ligament reconstruction procedures for an injured knee, a graft ligament tunnel is usually formed through bones on both sides of the joint being repaired. A replacement ligament graft is then passed through the pre-formed tunnels of both bones until the replacement ligament graft extends through both bones. Both ends of the ligament graft are then secured to the bones under tension across the joint in order to tie the two bones together in a manner that mimics the torn or broken ligament being repaired or replaced.
In the past, ligaments have been secured to the bones by means of surgical stables, screws or buttons. A problem with using staples and conventional buttons to attach both ends of a ligament graft to a bone is that both require two incisions. Once in place, staples are not easily removed in the case where adjustments are necessary. Staple removal could subject the bone to undue trauma and even result in mutilation of the bone. In addition, the graft ligament can sometimes slip out from under the staple by working its way loose. While buttons tend to be easier to remove in the case where adjustments are necessary, adjustments thereto requires severing or untying of the cords or sutures securing the ligament graft to the button and then retying of the sutures.
A variation of the surgical button known as an "ENDOBUTTON" can be used in a manner that allows for a single incision to made. The ENDOBUTTON consists of a small beam-like elongated button that can be inserted through a bone tunnel using sutures rather than a second incision, which is an improvement over ordinary surgical buttons in this regard. However, ENDOBUTTONS, like all buttons, require a suture link with the tendon or ligament graft, which provides for a more flexible and elastic linkage between the bone and tissue graft. The knot in the suture used to attach the tissue graft and ENDOBUTTON requires a knot, which introduces a certain level of risk of failure and requires proper tying to avoid risk of knot failure. Moreover, the inherent elasticity of a suture linkage results in a less rigid and secure linkage, which can decrease the ability of the tissue graft to form a strong biological adhesion or fusion with the bone tunnel. This can have both short-term and long-term negative consequences.
Finally, endosteal interference screws have the limitation of being attached to soft interior bone rather than the hard cortical bone surface. In addition, interference screws provide a considerably smaller surface area within the bone hole for biological healing and attachment of the ligament graft. This is because interference screw tends to push the ligament graft to one side of the hole, with the majority of volume within the hole being occupied by the screw. This can result in a less secure biological bond compared to other securement methods that allow for the ligament graft to make contact with more of the bone hole surface. Since the quality of bone in the tunnel is highly variable, the standard deviation of pullout strength is greatly increased in the case where interference screws are employed.
Many other procedures and devices have been developed for attaching a replacement ligament graft to bone. However, many have not proven adequate and have raised serious issues with respect to the strength, stiffness, and reliability of the ligament graft. Each of these raise important issues as to the clinical success of the procedure. In addition, many of the more innovative devices and procedures require complicated tooling.
U.S. Pat. No. 4,997,433 to Goble et al. discloses an alternative anchor device for mounting a ligament within a bone tunnel under tension. The Goble et al. device consists of a pair of stud arms defining a space at the rearward end for longitudinal receipt of a ligament end and a cylindrical stud having a hook edge at a forward end. The ligament is secured between the stud arms by means of screws, preferably in combination with a bone plug that acts as a stiffening aid. A major problem with the stud arms is that they are interposed between the ligament graft and the bone tunnel, which diminishes the overall surface area contact between the ligament graft and bone tunnel wall. This results in a substantial reduction of the tendency to form a biological bond over a large surface area of the graft ligament and the bone tunnel wall, thus compromising the long term strength and stability of the graft.
The forward end having the hook edge is compressible due to a longitudinal slot running therethrough, which allows the hook edge to be flexed or compressed inwardly against a spring-like resistance to allow for passage through a ligament tunnel. The Goble et al. device is installed by pulling the stud connected to the ligament end through the ligament tunnel, with the angled top of the hook edge acting as a camming surface that causes the hook end to compress inwardly to allow passage through the ligament tunnel. Because of the spring-like resilience of the Goble et al. device, the forward end springs outwardly back to its uncompressed state as the hook end emerges from the ligament tunnel, which causes the hook end to extend over and engage the bone cortex.
Because the forward end requires sufficient spreading force to reliably ensure that the hook end is, in fact, forced to expand outwardly by its own internal spring-driven power without any external mechanical assistance, the hook end is necessarily caused to push with substantial force against the ligament tunnel wall. Hence, although Goble et al. purports to teach the use of sutures to deploy the Goble et al. stud, in practice a threaded tool that screws into a corresponding threaded female portion of the Goble et al. stud is required to apply the force necessary to reliably force the device through the ligament tunnel. Use of this special tool adds an additional level of invasiveness and difficulty into the procedure.
In view of the foregoing, there exists a need for a simple, more easily deployed anchor device that could securely attach a bodily tissue such as a replacement ligament graft to a bone.
It would be an additional improvement in the art if such anchor device could be reliably deployed while minimizing the invasiveness of the surgery, particularly the number of incisions that would have to be made to deploy the anchor device.
In addition, it would be an advancement in the art to provide an improved anchor device that included a mechanism that provided a discernable signal or means to indicate when the anchor device has been successfully deployed and securely engaged within the bone.
It would be a further improvement in the art to provide an anchor device that allowed for broad surface contact between the graft tissue and the inner surface of the bone tunnel in order to increase the biological bond and provide a stronger, more reliable connection with the bone.
It would yet be an improvement in the art if such anchor device could be easily molded from a bio-absorbable material.
Such anchor devices for reliably and securely mounting bodily tissues such as ligaments and tendons to a bone are disclosed and claimed herein.